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PSB4860

Digital Answering Machine with Full Duplex Speakerphone SAM EC

Siemens AG 

PSB 4860

Functional Description

Table 6 Attenuation Control Unit Parameters

Parameter # of bytes Range

Comment

TW

1

ATT

1

16 ms to 4 s

0 to 95 dB

TW to return to idle state

Attenuation for GHX and GHR

DS

1

0.6 to 680 ms/dB Decay Speed (to idle state)

SW

1

0.0052 to 10 ms/dB Decay Rate (used for TSW)

Note: In addition, attenuation is also influenced by the Automatic Gain Control stages

(AGCX, AGCR) in order to keep the total loop attenuation constant.

2.1.3.4 Echo Suppression Status Output

The PSB 4860 can report the current state of the echo suppression unit to ease

optimization of the parameter set of the echo suppression unit. In this case the SPS0 and

SPS1 pins are set according to table 7.

Table 7

SPS0

0

0

1

1

SPS Output Encoding

SPS1 Echo Suppression Unit State

0 no echo suppression operation

1 receive

0 transmit

1 idle

Furthermore the controller can read the current value of the SPS pins by reading register

SPSCTL.

2.1.3.5 Loudhearing

The speakerphone unit can also be used for controlled loudhearing. If enabled in

loudhearing mode, the loudspeaker amplifier of the PSB 4851 (ALS) is used instead of

GHR (figure 15) when appropriate to avoid oscillation. In order to enable this feature, the

PSB 4851 must be programmed to allow ALS override. The ALS field within the AFE

control register AFECTL defines the value sent to the PSB 4851 if attenuation is

necessary (see specification of the PSB 4851).

2.1.3.6 Automatic Gain Control

The echo suppression unit has two identical automatic gain control units (AGCX,

AGCR).

Semiconductor Group

38

10.97

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